VO2-switched broadband and quadruple-band terahertz metamaterial near-perfect absorber

Abstract We propose a hybrid design featuring a plasmonic grating-assisted vanadium dioxide (VO2) metamaterial to create a THz absorber capable of switchable broadband and quadruple - band near - perfect absorption. When VO₂ is in the metallic phase, the structure acts as a metal-insulator-metal (MIM) absorber, covering a wide range of 3.0 to 6.1 THz at absorption efficiency beyond 90% due to the electrical and magnetic resonance between the two metallic VO2 layers. By adjusting of the phase transition of VO2 to the dielectric state, the structure manifests as a plasmonic grating coated with a dielectric layer, generating quadruple-band near-perfect absorption via guided-mode resonance (GMR) and cavity-mode resonance (CMR). The broadband absorption and quadruple-band absorption are both insensitive to the incident polarization and the broadband displays wide incident angle stability (60̊). Furthermore, the quadruple-band absorber exhibits superior sensing performance with high refractive index sensitivity (3.5 THz/RIU) and a quality factor (243.1). This bifunctional and adjustable metamaterial device exhibits substantial promise for use in terahertz technologies, serving as smart absorbers and liquid sensors.